Fig. 3. RGC axon navigation in wild-type and Foxg1^-/- embryos visualised by anterograde tract tracing at (A-E) E13.5 and (F-L) E15.5. For each age, progressively more caudal coronal sections of an individual embryo show injections of DiI (red asterisks) (A,F) in wild-type eye (e) and (D,I) in mutant eye; (B,G,D,I) labelling of optic nerve (on) and optic chiasm (oc); and (C,H,E,J) labelling of optic tracts (ot). (C,H) In the wild-type optic tracts, contralateral labelling is stronger than the ipsilateral labelling (white arrows). (E,J) In the mutant optic tracts, ipsilateral labelling appears stronger (white arrows). (K,L) Horizontal sections of embryos in which DiI was injected into one eye and DiA into the other eye of (K) an E15.5 wild-type and (L) an E15.5 Foxg1^-/- embryo (ventral midline is marked by broken white line). (K') Horizontal sections of the wild-type optic tract, growing over the diencephalon, from the same embryo as in K showing that each optic tract is predominantly labelled with dye from the contralateral (con) eye, although some ipsilateral (ips) label is also detectable (appears yellow where dyes overlap). (L') Horizontal sections of the mutant optic tract from the same embryo as in L, showing abnormally high levels of red label from the ipsilateral eye. Scale bars: 500 µm in A-E; 650 µm in F-J; 100 µm in K,K',L,L'.